Image forming apparatuses such as a copy machines and laser beam printers have a conveyance path through which a flexible, sheet-like medium such as paper is conveyed and moved. When designing the conveyance path, the behavior of a flexible medium which moves through the conveyance path is analyzed by a computer simulation, and rendered on a screen in order to shorten the development period and reduce cost.
Various simulation techniques have been proposed.
For example, there are known techniques of evaluating the conveyance resistance and abutment angle of a flexible medium with respect to a conveyance member (PLT1 and PLT2). More specifically, a flexible medium is expressed by finite elements according to a finite element method. Contact of the flexible medium with conveyance members such as a guide and roller in the conveyance path is determined, and the equation of motion is numerically solved.
There is also known a technique of more simply expressing a flexible medium using masses and springs to increase the calculation speed.
As for analysis of the motion of a flexible medium, Newmark β method, Wilson θ method, Euler method, Kutta-Merson method, and the like are widely known. In these methods, the equation of motion of a flexible medium which is discretely expressed by finite elements or mass-spring systems is formulated. The analysis time is divided into time steps each having a finite span. An unknown acceleration, speed, and displacement are sequentially obtained from time 0 for each time step. In other words, numerical time integration is performed. In motion calculation of a flexible medium, the flexible medium is divided into rigid elements. A flexible medium model is created by coupling the rigid elements with springs. By using this model, calculation is done on the assumption that a force proportional to a displacement from an original shape is generated. That is, calculation is executed on the premise that the original shape is a shape rendered as an initial shape, and if it is deformed by an external force, a restoring force acts to restore the shape.
In general, the sectional shape of a flexible medium is linear when the flexible medium is set in an image forming apparatus such as a copy machine. Thus, the initial shape of a flexible medium is defined as a linear shape, and behavior calculation starts from a state in which the restoring force is 0. However, the calculation load and model scale increase if the entire conveyance path is simulated at once from paper feed to discharge for each model.
To prevent this, the following technique is proposed (PLT3). More specifically, only a part to be evaluated is extracted from the entire conveyance path. A flexible medium is arranged in conformity with the extracted conveyance path. The restoring force acts at the start of calculation, the initial shape of paper is calculated, and then a conveyance calculation is performed.